Sound reproducing system



y 1935- E. R. HENTSCHEL 7 2,000,840

' SOUND REPRODUCING SYSTEM Eiled May 25, 1930 2 Sheets-Sheet 1 'IIE- E INVENTOR. V H V /t vw/al' 6L modefi BY H /'\A 1 15. E b ETORNEY May 7, 1935.

E. R. HE'NTSCHEL SOUND REPRODUCING SYSTEM Filed May 23, 1950 Wk Q IN V EN TOR.

AT RNEY;

Patented May 7 1935 i I t e UNITED STATES PATENT l OFFICE;

h 7 2,000,s4. o H e SOUND REPRODUCING SYSTEM Ernest R. Hentschel, Washington, D. 0.; John Olson, administrator of said Ernest R. Hentschel, deceased, assignor to Wired Radio, Inc., New York N. Y., a corporation of Delaware Application May'23, 1930, Serial No. 455,132

' 3 Claims. (01. 250-22) My invention relates broadly to signal receivthe local source of alternating current at the re. ing systems and more particularly to a circuit ceiver. The soundreproducing deviceconstitutes arrangement for a signal reproducingsystem. a. condenser'whose capacity varies as the ele'ctroe.

One ofthe objects of myinvention is to provide static speaker operates. This continuous v'a'ria "5 a circuit arrangement for a sound reproducing apmen in p y mally tends to affect the Ge paratus i signalreceiving System; stancy of frequency of theoscillator at the re- Another object of my invention is to providea eeiver- H v r by p 'g a multipli .circuit arrangement for an electrostatically oper- Selective Circuits between the oscillator a 451137 ated sound reproducer in a radio receiving system. S d reproducing device; undesired r action s 'Still another object of my invention is to provide n d- Y T I a 10 a system for mechanically heterodyning radio fre- Referring to Fiesg and '2 reference Ie t 'A quency currents for the reproduction of signals r n a a e g d fastened to 591118 in: a radio waiver. solid point as at C1 and C2 by insulating brackets ;A'iurther object of my invention is to provide a F a thin light conducting Plate mounted t circuit arrangement for a mechanical detector in a Slight movement toward away from Plate 5 Q a radio receiving system responsive to continuous A I l fn of flex b i e e ine gFT' i n wave energy; WhlCh lIl turn are "shown fastened to a sta- Other and further objects of my invention re tlonalfy 83 D and E are m a y sidein the circuitarrangement fora signal receiv charges and from plates A d- 13.111959 ing system as set fo'rthmore fully in the specifica- Plates a chargedffrom two f i g?" 20 tion hereinafter following by reference to the acmg u e p em fi companymg drawings in which: 7 there W111 be only a steady attraction or repuls- Figure 1 is a cross-sectional view through one i gg p g f 2 gg iigg ggi gfiggz z g gg form of the mechanical detector of my invention, alternate attraction. repulsion; and .plate F 7 Fig. 2 is a front elevation of the detector illustrated in Fig. 1; Fig. 3 shows a set of characteristic curves for explaining the theory of operation of the mechanical detector illustrated in Figs, 1 r and 2; Fig. 4 shows a circuit arrangement for the apparatus including the mechanical'detector sys- 'tem of my invention; and Figs. 5a and 5b illustrate a set of characteristic curves describingthe theory of operation of my invention. The circuits of my invention provide means for producing mechanical'vibration by the interaction of the incoming signaling energy with local both electromotive forces are inphase, so there source oscillations? the d response bging would be a' repulsion between plates-A and F; "At Y determmed'by the construction of the mechanical time JV and M th two are-ulsodegrees out of will vibrate. The frequency of i this mechanical vibration will be equaljto the difierence between the two radio frequencies.

The actionfis illustrated inFig. 3 which shows I two sinej electromotiveiforces. The electromo'tive 30 .force of the upper curve, passes throughfive cyI- cles While that of the .lower passes through four. Electromotive force :is 'used instead of current because wires D and]?! are connected to points of greatest electromotive'f orce for best operation. At the time represented by I and L,

40 system in the form of an electrostatically actuated phase 50 there would be an attraction; AtK and 0" sound reproducer. In the system of my invention N they are again in phaseeso there-15.3 repulsidn I provide an electrostatic sound reproducer ina the mechanical cycle;isfimshed eluding Stationary plate and a a l plate In Fig.4 I have shown the circuit .arrangemen disposed adjacent there-to- Alternating current for theireceivingapparatus of my-invention in' of different frequencies is applied to the individual which an a t nna and ground circuit is illus-.- 45' plates resulting in alternate retraction and repul t t by reference characters I and la to which sion and vibration of the movable plate at a freis co a radio frequency amplifie com I I quency' equal to the difference'betweenthe applied t t t y le tron t b '2 a d, 3 hi h r frequencies. The tone of the signal reproduction l ti l t d t the in in i nal i fr emay be' determined by the physical properties of quencybymeans of circuits 2a and 3a;for delivere 5d the-sound reproducer. I have found that in aping energy tothe tank circuit 4. An oscillator 5 plying the alternating current to the electrodes is l provided having coupling'coils 8'fand 10 in constituting the electrostatic sound reproducer the input and output circuitsthereof [tuned by that it is important to prevent reactionfrom' the means of. variable condenserfs'y'stem. .|.l The x operation of the'sound-reproducing device upon oscillatormay bevariably coupled byrcoupling' '55,

coil 8 which'is coupled with inductance 9 in the input circuit of the radio frequency amplifier which includes tubes 6 and I. The tank circuit I2 is connected in the output circuit of the radio frequency amplifier constituted by tubes 6 and 1 and interstage tuning of the amplifier is obtained by adjustment of circuits 6a and 1a. Screen grid tubes are employed in the several radio fre' quency amplifier stages for the elimination of undesired capacity coupling. The power supply for the several circuits is obtained from any suitable source which I have represented by reference character l5, common to the circuits of the oscillator 5 and the circuits of both of the radio frequency amplifier systems which operate at different frequencies. .By eliminating capacity coupling in the several circuits the separate channels may be operated at 1 different frequencies in close proximity one to the other for impressing upon the speaker system it alternating current charges at different frequencies. That is, a, connection is taken to the fixed electrode A from tank circuit 12 by means of connection l3. Connection is taken to the flexible diaphragm F by means of lead 1'4 which connects 't'otank circuit 4. By adjusting the tank circuits 4 and I2 theivoltages are applied to the plates A andF in suchrelation as to produce the desired tone at the receiver. I

For'instance, if a 1000 cycle note is desired,

the local oscillator frequency should be either I000 cycles, that is, one kilocycle,,higher or lower than that of the incoming signal, as plate F vibrates at a frequency equal to the difference between the two radio' frequencies. If both plates are of light construction, and both flexibly suspended, then both plates would vibrate, being attracted towards each other'at'the time when there is 180 difference in phase between the two electromotive forces, and repelling each other when the two are in phase, phase difference.

The amplifier 6-4 segregates the oscillator from the speaker system for preventing reaction of the varying capacity at the speaker system upon the oscillator, thereby preventing any tendency of the oscillator to change the constant modulated by a system which produces variations in the frequency of the carrierwave, then these variations produce corresponding motion in the plate F. For instance, if the transmitter frequency were 1,001,000 cycles and the local oscillator frequency, circuits 5, 8, l 0, I I, were 1,000,000, we would have a 1,000 'cyclenote. If now the transmitter changes to 1,002,000, there would be a 2,000 cycle note produced, and if it had changed to 1,000,050, plate F would be vibrating 50 times per second. 7

The systemof my invention is adaptable to broadcast reception by adjusting the frequency of oscillator 5 to the frequency of the transmitter. Under these conditions an electromotive force is produced on fixed plate A through lead I3 from tank circuit I2 represented by curve 0 in Fig; 5a. The incoming signaling energy produces a charge on the movable plate F designated by curve P and as the electromotive force between the two plates varies the repelling force varies and motion is produced. A condition of zero phase relation of the incoming energy with respect to the locally produced energy at the same frequency has been illustrated in curve 5a; In curve 52) a 180 phase relationship is assumed and there is a constant attraction between the .plates A' and F and the variations in amplitude of the received signal will cause a variation in the attraction between the plates.

In operation the electrostatic device has many advantages over electromagnetic forms of sound reproducers, among which may be mentioned improved tone quality, cheapness in manufacture and production, and. simplified assembly of the parts constituting'the loud speaker construction.

While I have described one of the preferred embodiments of my invention, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other-than are imposed by the scope of the appended claims. I

What Iclaim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a sound reproducing system an electrostatic sound reproducer comprising a pair of electrodes disposed in parallel relation and movable in respect to each other, a source of received radio frequency oscillations, a local source of radio frequency oscillations, a radio frequency amplifier having its input connected to said source of received oscillations, a tuned circuit comprising an inductance and a capacity connected in the output circuit of said amplifier, a second radio frequency amplifier having its input connected to said local source of radio frequency oscillations, a'second independent tuned circuit comprising inductance and capacity connected in the output circuit of said second amplifier, and means including connections between the electrodes of said sound 'reproducer and suitable points in each of said tuned circuits for applying to each of said electrodes individually an oscillating potential of the particular frequency produced in the tuned circuit to which it is connected, whereby a beat frequency electrostatic reaction between said electrodes is obtained.

2. In a sound reproducing system, an electrostatic sound reproducer comprising a'fixed electrode and a flexible electrode disposed in parallel relation, a source of received radio frequency oscillations, a local source of radio frequency oscillations, a radio frequencyamplifier having its input connected to said source of received oscillations, a tuned circuit comprising inductance and capacity connected in the output circuit of said amplifier, a second radio frequency amplifier having its input connected to said local source of radio frequency oscillations, at second independent tuned circuit comprising inductance and capacity connected in the output circuit of said second amplifier, and means including connections between the electrodes of said sound reproducer and suitable points in each-of said tuned circuit for applying to each of said electrodes individually an oscillating potential of the particular frequency produced in the tuned circuit to which it is connected, whereby a beat fre-v quency electrostatic reaction between said electrodes is obtained.

3. In a device of the class described, an electrostatic sound reproducer including a pair of electrodes disposed in parallel relation to one another,

a, channel responsive to moduirequency energy, amplifying means in said signal receiving channel, a local source signaling energy and the energy from the local source of oscillations independently upon said electrodes whereby an electrostatic beat frequency interaction between said electrodes becomes effective for the reproduction of sound.

ERNEST R. mom. 

